I'm currently working on a 400 Serial 51868U ( http://www.audiokarma.org/forums/showthread.php?t=559395 ) but have no scope. So I asked Dave Gillespie if there was a way to adjust the P.I. without the aid of a scope and not involving math higher than 7th grade. Dave came to the rescue! He actually came up with 2 ways of doing it, although the 1st involves some math (no real way of getting around it), and it works. I found the 2nd option a faster and easier way to do it, and really even a Caveman can do it. With BOTH OPTIONS the Unit under adjustment is UNPOWERED and UNPLUGGED! REMEMBER ! UNPLUG IT FROM THE WALL. The Resistor # in parenthesis is the RIGHT CHANNEL. Unparenthesis is LEFT CHANNEL! Resistor #'s are based on the 48001 and up manual. Units with a serial # lower than 48001 will use the 20001 and up manual. From what I understand the 20001-29999 manual follows the 10001-19999 manual for part numbering. My copy of the 10001 manual does NOT have a schematic. But the parts lists match up for these parts and the caps below in the improved option. 48001.......20001 R110 = R87 Right Channel R116 = R97 Right Channel R109 = R86 Left Channel R115 = R96 Left Channel THESE INSTRUCTIONS ARE FOR THE 400. For OTHER MODELS SEE the note dated 10-17-14 for clarification and further instructions. 1st OPTION... 1.) Measure and record the value of R110(R109). 2.) Disconnect one end of R116(R115). Measure R116(R115) and record. Do not reconnect yet. 3.) Determine what value resistance when in parallel with measured value of R116(R115) equals the measured value of R110(R109). 4.) Place ohm meter from pin #3 of phase inverter to ground. 5.) Adjust phase inverter for value determined in step #2. 6.) Reconnect R116(R115). NEW AND IMPROVED way, and the way I did it. This involves no desoldering, soldering, or math. Just a DMM and a Jumper wire with 2 alligator clips. AGAIN! TURNED OFF AND UNPLUGGED!!!! NOTE: PART #'s change due to SERIAL #'s. For those having units with serials of 29999 and below, the relevent part #'s the B+ to Ground is C75C. For those having units with Serials 48001 and above, the relevent part # of the B+ to Ground is C52C. It's the SAME PART Just uses different part # on the schematics. 1.) Using an alligator clip lead, short the B+ supply point to the phase inverter tubes to ground. This would be the 320V source that appears across C52C. This is the 4 section CAN CAP. 2.) Ground the common lead of your ohm meter. 3.) Measure and record the resistance value that appears at pin #1 of the left and right phase inverter tubes. 4.) Connect your ohm meter to pin #3 of the left and right phase inverter tubes, and adjust their respective phase inverter control for the respective value noted in Step #3 above. 5.) Remove the alligator clip lead. Close it up and enjoy. It took me 5 minutes total to adjust the PI on both sides with original pots. Actually it took me longer to clean them with DeOxit than it did to adjust them. They can be touchy but making a mark on the dial and face 1st, then spray conservatively with DeOxit, and exercise 40-50 times. Blow it dry (cool setting on lungs) and do your adjustments. A very Big thanks to Dave Gillespie. I hereby nominate him for FISHER Forum M.O.T.Y. Any seconds??? Larry I pulled the info for the 500 and 800 models from post 19 to consolidate the info. (07/31/2014)EDIT:Changes to 400 procedure for 800-B/C and 500-B/C The only real changes are which can capacitor and which section of that can cap to ground to take the measurement off pin 1 of the phase inverter tubes. It's the same section. Depending on which model you have, the B+ will either be 320VDC or 350VDC. As the 2nd option is the most efficacious for those of us who are technically challenged, we'll use that one for all of the following models. POWER OFF, PLUG BAGGED!!!! (this keeps you vertical!) 800-C STAND-ALONE SERVICE MANUAL ALL VERSIONS 1.) Ground C87C and follow the rest of the directions. C87C is the 350V B+. (Marker B3 at capacitor and B1 at V12) EXECUTIVE VIII Model 950 (800-C Serial 10001-19999) Procedure is same as Standalone 800-C. B+ on C87C is 320V tho. EXECUTIVE IX Model 960 (No Serial noted on manual). Procedure is same as Standalone 800-C. B+ on C87C is back up to 350VDC. 500-C 30001-49999 manual Ground C91C(350V B+) and follow directions outlined in POST #1 500-B 20001-29999 manual Ground C78C (320V B+) and follow directions outlined in POST #1 800-B 20001-29999 manual Ground C95C (320V) and follow directions outlined in POST #1 EDIT 10-17-14 NOTE: For those with units other than the 400. You may find that appears that Pins 1 & 3 actions are reversed. Or 6&8 are the actionable pins, Or that on certain units (with the 7199 driver) Pin 1 & 8 are the pins used. See POST #29 by Dave Gillespie for the explanation and solutions to this. POST # 30 will LIST by MODEL which pins are which.